The problem appears to be how you have the name setup on the download ...

/byggerod.pdf.zip

First, you have the extra slash in the name and then you have the double ending on the filename of .pdf.zip

Try using instead:
byggerod.zip

and be sure to rename the file on the server ...

The file should also be in the:
/download

directory for this ...

Be sure that /pub is set to 777 ...